1. Related Technical Fields
Related technical fields include image recognition apparatuses, methods and programs for acquiring image information including at least an image of a road surface in an area close to a vehicle, and determining the type of a lane mark included in the image information by performing an image recognition process on the acquired image information.
2. Related Art
In recent years, in fields of navigation apparatuses and vehicle control apparatuses, various techniques have been developed to recognize various types of lane marks such as solid-line or broken-line lane marks disposed on road surfaces, and the techniques are used to recognize and maintain a vehicle within a lane in which a vehicle is running, and so on.
As one of techniques associated with the lane mark recognition, for example, a running lane recognition apparatus is disclosed in Japanese Unexamined Patent Application Publication No. 2005-322166. In this running lane recognition apparatus, an image is taken and the image is converted into a plan-view image of a road viewed from above by performing a coordinate transformation process. Thereafter, using the plan-view image, lane mark lengths are determined for lane marks detected in two areas defined in the plan-view image, wherein the two areas are defined as adjacent locations in the same direction as the running direction of the vehicle. If the lengths detected for the lane marks are greater than a predetermined value in both areas, it is determined that the lane marks are solid lines. In a case where the lane mark lengths are greater than the predetermined value only in one of the two areas, it is determined that the lane mark is a broken line. In a case where the lengths are smaller than the predetermined value in both areas, it is determined that there is no lane mark. According to the determination result as to the type of the lane mark, the running lane recognition apparatus determines the lane in which the vehicle is running.
Another example of a running lane recognition apparatus is disclosed in Japanese Unexamined Patent Application Publication No. 2007-200191. In this running lane recognition apparatus, as in the apparatus disclosed in the Japanese Unexamined Patent Application Publication No. 2005-322166, a coordinate transformation process is first performed to convert an image into a plan-view image of a road viewed from above. Thereafter, a plurality of lane detection areas are set in one frame of plan-view image, and the integral intensity is calculated for each area. If the calculated integral intensity is substantially constant for the plurality of areas, it is determined that the lane mark of interest is a solid line. On the other hand, if the integral intensity calculated for a plurality of areas varies with time and from one area to another, it is determined that the lane mark of interest is a broken line. On the basis of the result of the determination as to the type of the lane mark, the running lane recognition apparatus determines a lane in which a vehicle of a user is running.